AndyT

anyone have a link or a calcualtion to get the correct size slicks i'd need ?

currently running 245-40-18 in the front 315-30-18 in the rear


thanks

Geoffrey

Are you talking about maintaining the proper diameter to keep the ABS happy and the AWD functioning properly?

AndyT

yes exactly , also keeping them as wide as my current tires so they don;t rub. mine barely make it.

Larry Herman

Andy, it's really not hard. Almost all race tires are spec'd in diameter and width, not aspect ratio. You just need the MFGs tire specs for your R compounds. For example, Hoosier R6 245/40/18s are 9.3" in tread width and 25.7" in diameter. That converts to 236 mm and 652mm. An equivilent Pirelli slick would be the 245/645-18. Michelins are measured in centimeters, so they would be a 24/65-18.

AndyT

thank you. I wan thinking of running these in DE events and Trackmasters, etc. I'd stick to the Hoosiers for Club racing.. Or maybe jsut gut the car out and run in GT1R. Yikes !!! Scary thought : )

AndyT

check this converter out

http://www.dakota-truck.net/TIRECALC/tirecalc.html

AndyT

pardon my retardedness.

so for Pirellis I'd want

245/645/18 up front
305/645/18 in the back

645 is the overall diameter so i am dead even front to back correct ?
tread width is 249 and 300 per the website

Geoffrey

yes, those would be the correct sizes for your car.

AndyT

thank you Gurus : )

John H

I think but am not sure but switching back and forth is a PITA. IIRC slicks don't want or need as much camber as Hoosiers so everytime you switch back and forth you'd really need an alignment. At least that is what I was told after trying to run Hoosier Cup slicks on my 993 with the maximum camber one can get and stay in the stock class. It pushed so bad it was undriveable.

Slicks are noticeably better under braking though.

Joe Weinstein

Hi folks. danger danger. Never, never use any online 'tire size calculator'
if you are dealing with close tolerances, such as trying to prevent rubbing,
or if you need precise diameter info, especially if you're dealing with
race tires. They all mean well, and are simply designed according to what
the tire size nomenclature is *supposed* to mean, but in the real world
there is a wide range of variance between what a tire is designated as
and what it's real dimensions are. For the real facts you *have* to go to
the tire manufacturers spec sheet. I have seen two different 245/45-16
tires differ in diameter by 1/2 inch *from the same manufacturer*! They
were just different model tires. Recently Hoosier stopped making it's
A06 305/30-18 tire. Now they list a 315/30-18. *It's the same tire*! They
just decided that the actual tire dimensions were closer to the 315 meaning,
so after 6 years they just changed what was printed on the sidewall.

Joe Weinstein

AndyT

Joe I have old 305s and new 315 Hoosiers It's true and annouying. I was running 245/35s up front to match the 305s and in reality I should have been running the 245/40s the whole time !!!

thanks for the advice !

95m3racer

Also realize that different tire manufacturers have different "actual sizes" than whats printed on the tire. Also measure the tire in real life with a measuring string and be as accurate as possible, especially for Data logging purposes.

38D

Andy I would not run slicks at DEs -- it is an utter waste. You'll have way too much cornering speed relative to the group, so you'll rarely get to go ful bore thru a corner. It gets old real fast.

kurt M

Simple fix to that is only run 90 HP while driving in the instructors groups then you need all you can get just to keep from becoming road kill. The up side is the tires last 2X as long.

Question to the gurus. I have been running the Hoosier cup slicks after getting hold of a P/U truck load of take offs. What camber do they require? I set the car up to Hoosier DOTs and have not changed anything after going to the Cups.

BTW the cups have the sharpest drop off I have ever seenn in a track tire. They go from Good Grip to "Good God, there is something wrong with the car" bad all at once. They turn to goo even when cool when they go off.